Resistance element



June 6, 1933. R. E. GRAF 1,913,272

RESISTANCE ELEMENT Filed Oct. 4, 1929 ATTORNEYS.

/4 filo /a w I INVENTOR. l R06 er? ifiraf BY /5 I7 01 .5. 5 2. q gag Patented June 6, 1933 UNITED STATES PATENT OFFICE ROBERT E. GRAF, OF CLEVELAND, OHIO, ASSIGNOR TO THE OHIO CARBON COMPANY, OF CLEVELAND, OHIO, A CORIORATION OF OHIO RESISTANCE ELEMENT The present invention relates, as indicated, to a resistance element and method of making the same. The primary object of the invention is to provide an article of the class described which will be efficient for its work and in which a proper electrical connection will be provided between the resistance element proper and the terminals therefor. A further object of the invention is to provide a device of the class described in which the terminals are more securely at-. tached to the resistance element proper than has been done in the past. A further object of the invention is to provide a simple and efiicient method of manufacturing an article of the class described. Further objects of the invention will appear as the description proceeds. To the accomplishment of the foregoing and related ends, said invention, then, consists of the means hereinafter fully described and particularly pointed out in the claims.

The annexed drawing and the following description set forth in detail certain mechanism embodying the invention, such disclosed means constituting, however, but one of various mechanical forms in which the Y principle of the invention may be used.

In said annexed drawing: Fig. 1 1s a perspective new of a resistance element formed in accordance with the present invention; Fig. 2*is a vertical section thereof; Fig. 3 is a sectional view taken substantially on the line 33 of Fig. 2; Fig. 4 is a perspective view of a terminal; and

Fig. 5 is a view similar to Fig. 2 but showing four wires having portions of varying shapes embedded in the resistance element.

Referring more particularly to the drawing, it will be seen that the resistance element proper comprises a bar or block 10 of molded carbon. It is to be understood that the term molded carbon is to be interpreted in accordance with its use in the ractical art to mean a mixture of finely divided carbon and a binder, inert material being include in the mixture if desired and in the quantities desired to achieve the desired resistant value. Of course it is to be further understood that my invention includes the use of molded bars or blocks of resistant material other than carbon, and such claims as do not specify carbon are to be read with this understanding. A pair of conducting terminals 11 and 12 are mounted at the opposite ends of said bar 10. Each of said terminals comprises a wire having an end thereof formed as a coil, the axis of which is perpendicular to a plane including the axis of the wire proper. As will be clear from an inspection of Figs. 2 and 3, the coiled end of each wire is embedded in the bar 10, in such a position that the wires 11 and 12 are perpendicular to one plane including the axis of the bar 10, while the axes of the coils 13 lie in said plane. In other words, the axis of the coil is disposed at right angles. to the axis of the wire proper and to the axis of the bar 10, while the axis of each wire 11 and 12 is disposed at right angles to the axis of its coil 13 and to the axis of. the bar 10.

In manufacturing the device, the ends of the wires 11 and 12 are formed with the coils 13. A quantity of granular or crystalline carbon is then poured into a mold press together with a binder and any inert material which may be desired, and the wires 11 and 12 are inserted in said press, the coils 13 thereof being plunged into the mass of carbon. The wires 11 and 12 being suitably supported, the press is then operated to compress the mass to form the bar 10 with the coils 13 of the wires 11 and 12 embedded therein.

It is to be understood 'that most of the benefits of my invention may be obtained through the use of wires which are not formed with coils at their ends of the type above described, but the embedded portion of the wire should preferably be distorted so that the space in which the embedded portion of the wire is enclosed is not aligned with the protruding portion of the wire. Furthermore, it is not essential to m invention that the wires shall be embed ed only in the ends of the bar, but they may be embedded an where in the length of the bar, andd any esired number of wires may be use in Fig. 5, l have shown a block or bar 10' or" resistant material in which are mounted four wires providing five taps or terminals, and each of these wires is differently secured in said bar. Thus, the wire 14 is formed at its embedded end with a comparatively irregular coil 15 the axis of which is substantially aligned with the axis of the protruding portion of the wire 14. The wire 16 extends entirely through the bar 10, providing a tap or terminal at each extremity, and said wire is formed intermediate its ends and in the region embedded in the bar 10 with a simple curved portion 17 which is effective to prevent easy removal of the wire from the bar. The Wire 18 has its one end portion 19 bent at right angles to the protruding portion of the wire, and it will be obvious that the portion 19 provides an effective anchor. The wire 20 has its embedded end formed with a curved portion 21 similar to the portion 17 of the wire 16. These are examples of means which can be used to anchor the wires in place in the bar, but it is to be understood that the sole essential as to this is that the wire shall have its embedded end distorted to such an extent that the embedded portion or" the wire cannot be pulled out through a straight opening. 7

Other modes of applying the principle of my invention may be employed instead of the one explained, change being made as regards the mechanism herein disclosed, provided the means stated by any of the following claims or the equivalent of such stated means be employed.

1 therefore particularly point out and distinctly claim as my invention:

1. A resistance element comprising a bar of molded carbon, a wire, and a coil formed at one end of said wire, the axis of said coil being disposed substantially at right angles to the axis of said wire, and said coil being embedded in said bar and so disposed that the axes of said coil, wire and bar are mutually perpendicular.

.2. A resistance element comprising a bar of molded carbon, a wire, said wire including a curved portion imbedded in said bar, the axis of curvature of said portion being disposed substantially at right angles to the axis of said wire, said curved portion being so disposed that the axis of said curved portion, said wire and said bar are mutually perpendicular.

Signed by me this 1st day of October,

ROBERT E. GRAF. 

